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  • 1
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1399-3038
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Several studies have evaluated the value of cord blood IgE concentrations for predicting the risk of allergic disease in children. In all of these studies it is necessary to exclude cord blood samples in which the IgE may be falsely elevated due to admixing of maternal and fetal blood during parturition. The most common method for detecting mixing of fetal and maternal blood is measurement of cord blood IgA concentrations. We have examined the theoretical basis of IgA measurements for detecting maternal blood contamination and reexamined our own data to evaluate IgA measurements. Our data suggest that the average IgA concentration of 28. 2 μg/ml used in previous studies may not adequately exclude contaminated cord blood sample. Failure to reject contaminated cord blood samples would reduce the positive predictive value of cord btood IgE measurements.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Packed columns ; FTIR detection ; High press lightpipe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling of packed-column supercritical fluid chromatography (SFC) with Fourier-transform infrared spectrometry (FTIR) is demonstrated. The interface used for SFC-FTIR experiments is based on the lightpipe used for GC-FTIR, but it has been designed to withstand the high-pressure constraints of SFC. When used with beam condensing optics, this SFC-FTIR lightpipe flow cell has allowed detection limits as low as 270ng (3×Np-p) of injected acetophenone. Separation of a seven-component model mixture is shown on a silica bondedphase phenyl column. The on-line infrared spectra obtained are high-quality and readily identifiable. Spectral features of high-pressure carbon dioxide (subcritical vs. supercritical) are discussed with respect to infrared transparency in the flow cell SFC-FTIR experiment.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Packed columns ; On-line sampling ; Supercritical CO2 extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Packed column supercritical fluid chromatography, like HPLC, utilizes a sample loop to introduce materials onto the column for analysis. Unlike HPLC the mobile phase in SFC cannot be used to dissolve the sample. In practice, this causes a solvent peak, which can create a problem in the chromatographic interpretation. This paper describes one approach to solving this problem. A valving scheme is used to extract materials with the supercritical CO2 mobile phase and introduce them onto the column with no external handling. The viability of this method is demonstrated and separations of the CO2 extracts for several materials are shown on various columns. Comparisons are made for coal and coffee extracts using this on-line method and conventional off-line CH2Cl2 extracts. Advantages of the on-line procedure as they apply to chromatography and high information detectors are also discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 5919-5931 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photochemistry of methyl iodide adsorbed on Cu(110) surfaces has been studied using time-of-flight mass spectrometry, temperature programmed desorption, and retarding potential spectroscopy. The λ=337 nm photodissociation of CH3I adsorbed on clean and iodided Cu(110) is found to have an increased cross section (by ∼2 orders of magnitude) and altered dynamics from that of the gas phase at the same wavelength. On the clean Cu(110) surface both enhanced neutral photodissociation and charge-transfer photodissociation processes are observed, the latter being ascribed to hot photoelectrons generated in the substrate. On the Cu(110)–I surface, only enhanced neutral photodissociation is observed and the CH3I molecules are found to be orientationally ordered with a 20° tilt in the [11¯0] azimuth. Further evidence of altered neutral photodissociation dynamics is found in the observed I/I* branching ratio. In contrast to earlier studies of adsorbed CH3I, the branching ratio is found to favor the higher energy I* dissociation pathway as compared to the gas phase. The altered neutral photodissociation dynamics are ascribed to changes in the CH3I excited state potential energy surfaces, caused by interactions with the copper–iodine interface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background A family history of atopy, and cord blood immunoglobulin E concentration, have been shown to be predictors of atopic disease in children. Several studies have suggested that parental atopy may be related to newborn immunoglobulin E. Objective The purpose of our analysis was to evaluate whether parental history of allergic disease was associated with cord blood immunoglobulin E concentration. Methods The study subjects were from a defined population of 777 newborns delivered between 1987 and 1989. The mothers of these children completed a questionnaire during pregnancy concerning themselves and the child's father, including parental history of physician diagnosis of allergic diseases (allergies, hay fever and asthma). Total immunoglobulin E levels were quantitated in cord blood samples with an enzyme-hnked immunoassay.Results Median cord blood immunoglobulin E concentration was higher among infants whose mothers had a history of atopic disease, particularly for those with a history of asthma (P〈0.022) and allergen immunotherapy (P〈0.016) vs infants whose mothers had no history of any atopic disease. Comparing all babies with a maternal history of asthma, to babies where neither parent had a history of any atopic disease, the median cord blood immunoglobulin E was significantly higher (0.36IU/mL vs 0.21 IU/mL; P〈0.009). This association was found only among female infants (0.49IU/mL vs 0.20 IU/mL; P〈0.001).Conclusion Maternal, but not paternal, history of atopic disease was associated with an elevated immunoglobulin E among newborns. For maternal asthma, this association was only evident in infant girls.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Plasma-polyme rized (PP) coatings of chlorotrifluoroethylene (CTFE), tetraluoroethylene (TFE), and ethylene were deposited in a capacitively-coupled 13.56-MHz radio-frequency glow discharge on potassium bromide (KBr) infrared windows for moisture protection. The PPTFE coatings deposited slightly downstream of the internal plasma reactor electrodes provided the best moisture protection for the KBr windows. The PPTFE-coated windows tolerated an upper limit relative humidity of about 80 percent at 297°K without visible damage occurring to either window or coating within 24 h (86.4 ks). It appeared from environmental tests that some of the coatings failed to protect the KBr windows from moisture because of defects in the coatings (pinholes, cracks); others failed because of their high water permeability. Elemental analysis of the bulk and photoelectron spectroscopy (ESCA) of the surface of PPTFE coatings deposited downstream of the electrodes revealed that these samples contained less oxygen (from the atmosphere) than coatings deposited between the electrodes. The lower oxygen content of the coatings deposited downstream may have accounted for the improved moisture resistance of these coatings. The PPTFE coatings were posttreated by heating and by cross-linking with activated species of inert gases (CASING). Neither post-treatment technique was effective in improving the moisture resistance of the PPTFE coatings.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rates of calcium incorporation by selected tissues of Crassostrea virginica increased in a step-wise fashion from lowest values among organisms exposed to ambient total calcium concentrations of 45 mg l-1, intermediate values among oysters exposed to 135, 225, and 315 mg l-1, to highest rates for oysters exposed to 360 mg l-1. Although excised visceral mass tissue had highest rates of calcium incorporation relative to mantle, muscle, and both organic and inorganic portions of the shell, mantle tissue appeared to have the most dynamic response to changes in ambient calcium concentrations. Rates of dissolved calcium incorporation from ambient water were approximately two to three orders of magnitude higher than comparable rates from ingested algal food. Behavioral response to concentrations of selected inoic, species in the ambient environment may have been responsible for observed differences in rates of calcium incorporation.
    Type of Medium: Electronic Resource
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